Such bearing units are used also for disc coulters and are under particularly high strain due to the dust produced. They therefore have to be particularly well protected from dirt. In the case of pneumatic seed drills in particular, as well as fertiliser coulters, the bearing units are under particularly high strain because dust is also blown up and seed dressing agents or fertilisers can get to the bearing units as well. The seals are designed accordingly or several seals or cassette seals are used, which make the route to the balls and races of the bearing unit extremely long for any dust that gets in. These sealings need a wide installation space, making the amount of free space considerably smaller, especially when the lateral distances between the disc coulters are narrow. This frequently leads to blockages.
The objective of the invention is to create a bearing unit for a double disc coulter, containing a particularly good sealing, requiring little installation space and thus also ensuring a sufficient amount of free space between the individual disc coulters, even in the case of narrow distances between the rows of disc coulters.
The objective according to the present invention is achieved as described. Supplementary and alternative solutions being set out in an advantageous manner as claimed.
Through the provision of a double seal between the inner ring and the outer ring or on the outer ring race of the outer ring, the route to the balls is considerably extended for any dirt that gets in, without having to increase the distance between the disc coulters. This multi-stage sealing system does not make any additional installation space necessary, particularly in the axial direction of the bearing unit.
An advantageous execution of the invention is where the outer edge, facing away from the mounting flange, of the second, additional seal, has approximately the same distance to the mounting flange of the disc coulter as the outer edge of the seal arranged on the internal ring race of the outer ring. The existing seal between the outer ring and inner ring determines the necessary installation space of the bearing unit in axial direction. Through the outer edge of the second seal having roughly the same distance to the mounting flange of the disc coulter, the necessary installation space in axial direction is not increased despite the additional seal.
It is also provided for the inner ring to be connected to the coulter support of the disc coulter via the axis and the outer ring to be connected with the disc coulter via the mounting flange.
Sealing is particularly effective if the first seal is arranged in the gap formed by the inner ring, the outer ring as well as the protective cap and the cage. As the first component of the multi-stage seal, the seal sits within this gap, limited by the inner and outer ring on the one hand and the protective cap and cage or balls on the other hand.
As an alternative or supplement to this, it is provided for the second seal to be arranged in the gap formed by the outer ring and the protective cap. It is then located roughly within an extension of the borehole for the receiving of a screw serving for the attachment of the disc coulter and bearing unit and conveniently fills out this space also. Thanks to this multi-stage seal, a particularly compact bearing unit with a small installation space width can be realised.
In order to make a precise seating of the respective seals possible, it is provided for the seal to be positioned in a force fit between the inner ring and outer ring or outer ring and protective cap, meaning the seal is given its place and is held in its position at the same time. The outer ring and/or inner ring for the first seal provide a recess or projection in the gap for this purpose, giving the seal its forced fit or limiting the latter respectively. As regards the second seal between the outer ring and protective cap, this recess or projection is provided in the outer ring and/or the protective cap.
According to the present invention, it is also conceived for at least two additional seals to be arranged between the outer ring race and the protective cap, which are arranged one behind the other in the axial direction of the axis. Through the provision of several additional seals between the outer ring race and the outer housing, the route mentioned is extended even further, considerably improving the effect of the sealing of the bearing unit. This solution does not increase the necessary installation space mentioned in the axial direction of the axis either.
The present invention furthermore provides for the inner ring to be designed as a two-piece ring and consist of a first inner ring and a second inner ring, and for the part level to be located in the centre of the ball race in the case of a single-row ball bearing. This embodiment makes a backlash-free use of the bearing unit possible, which can also be used as a preloaded unit thanks to the divided inner ring.
A further embodiment of the invention is where the inner ring is designed as a two-piece ring and the part level is located between the races of the two rows of balls in the case of a double-row ball bearing.
The initial objective set can additionally be achieved through a first seal being arranged between the inner ring and the outer ring on the side opposite the mounting flange and a second seal being arranged, on the side opposite the mounting flange, between the outer ring and protective cap on the internal ring race of the outer ring.
With this embodiment, two seals are positioned one behind the other as a kind of seal package in order to ensure sealing between the inner ring and outer ring on the one hand, and between the outer ring and protective cap on the other hand. Looking from the direction of the ball or cage, a first, internal seal sits between the inner and outer ring here and a second, external seal between the outer ring and protective cap. In order to bridge the distances between the inner and outer ring and in order to stabilise the seals formed of flexible material, metal clips can be used, which form a common construction unit together with the seal.
Further details of the invention can be found in the figures and figure description.